This invention relates to lining of underground pipes, and in particular it relates to a new and improved liner and the method and apparatus for making same.
Underground pipes such as those used for water mains, gas pipelines, sewers and other service pipes deteriorate over time. It is known to rehabilitate such pipes by inserting therein a thermoplastic liner which is installed within the pipe, referred to as the xe2x80x9chostxe2x80x9d pipe in a reduced cross section shape and then forced by steam or other pressurized fluid to expand to its original shape, whereat it engages the wall of the host pipe to form a new leaktight passage for the flow of fluids therethrough.
A particular type of liner which has been found advantageous is one which, instead of being self-sustaining, relies on the residual strength of the host pipe. Because such pipes do in fact rely in part on the residual strength of the host pipe, they can be made with thinner walls than those which would be self-sustaining, although they must be of sufficient strength and thickness to securely span any holes in the host pipe, and of course strong enough and thick enough to subsequently perform the intended functions of the host pipe.
Arrangements for forming deformed liners for insertion in host pipes are shown in my prior U.S. Pat. No. 5,318,421 and in my prior European Patent No. 0 787 940 as well as in U.S. Pat. No. 4,207,130, PCT Published Application No. WO 87/03840 and United Kingdom Patent No. 1,580,438.
One of the more important problems associated with the use of a liner in a host pipe concerns protecting the deformed liner prior to and during insertion. Each abrasion which occurs prior and especially during insertion of the liner into the host pipe will limit the ability of the liner to expand within the host pipe and could adversely affect its leaktight integrity.
Several of the above identified patents disclose protecting a deformed liner with a sleeve which surrounds the deformed liner. However, as disclosed in these prior patents, the sleeve includes at least one seam line which provides a weakened location which could adversely affect the structural integrity of the sleeve before or during insertion in the host pipe, thereby exposing the liner itself to abrasions or the like before or during insertion into the host pipe.
Thus, there exists a need for improvements to better protect a deformed liner after it is deformed and then prior to or during insertion of the liner within a host pipe.
It is a purpose of the present invention to provide an improved liner of the type described which is deformed for insertion into a host pipe, together with a method and apparatus for making same, all of which overcome problems which existed in the prior art.
In accordance with the present invention, a deformed liner is, immediately upon deformation thereof, tightly surrounded with a coaxially extruded seamless protective sleeve.
In accordance with a preferred method and apparatus of the present invention, a thermoplastic material such as polyethylene is originally extruded in tubular form after which it is delivered to a deforming structure which may be of any known arrangement including the deforming structure as shown in my U.S. Pat. No. 5,318,421. The deformed liner then exits the deformer at ambient temperature. The extruded liner is preferably cooled after it is extruded and prior to the deforming apparatus. However, it is also possible to include cooling means within the deforming apparatus. As is shown in the prior patents, including my prior U.S. Pat. No. 5,318,421, the liner is deformed by deflecting it along a line running longitudinally along the periphery down into a U-shape which essentially reaches the opposite side of the periphery, leaving two rounded lobes on each side thereof, thereby providing a deformed structure which is generally referred to as heart-shaped. Immediately after such deformation, the deformed liner has some tendency to initially revert towards its original shape. At this moment, i.e., immediately after deformation, the deformed liner is passed through a tubular extrusion apparatus which extrudes a seamless tube coaxial with the liner closely about its periphery. The slight outward movement of the liner at this time will force it tightly against the coaxially extruded tube, which then becomes a high integrity seamless protective sleeve. The combined liner and protective sleeve may then be wound on a drum for transport to a remote location.
In accordance with a preferred embodiment of the present invention, there is provided a deformed heart-shaped liner in combination with a seamless protective sleeve which tightly surrounds the deformed liner, thus holding it in its deformed shape and protecting it against abrasions or the like.
In accordance with another feature of the present invention, ducts may be placed through the liner during the formation thereof. For example water ducts can be inserted therein to facilitate insertion of water to pressurize the liner to cause it to revert to its original shape after it has been inserted into the host pipe. Additionally, ducts may be provided either within the liner or in the U-shaped space between the liner and the sleeve for the passage of fiber optics or other service lines. If inserted between the liner and the sleeve, such ducts will ultimately be located, after reversion of the liner within the host pipe, in a tight space formed between the liner and the host pipe.
Thus, it is an object of the present invention to provide a new and improved liner, in combination with a seamless protective sleeve, for insertion into a host pipe.
It is another object of the present invention to provide an apparatus for providing a new and improved liner and protective sleeve combination.
It is another object of the present invention to provide a method for making an improved liner and seamless protective sleeve combination for insertion into a host pipe.